THE OPTX PROJECT. II. HARD X-RAY LUMINOSITY FUNCTIONS OF ACTIVE GALACTIC NUCLEI FOR<i>z</i>≲ 5

Yencho, Brian; Barger, A. J.; Trouille, Laura; Winter, L. M.

doi:10.1088/0004-637x/698/1/380

Cited by 83 publications

(133 citation statements)

References 58 publications

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“…We refer to this model as Luminosity And Density Evolution (LADE, see also e.g. Yencho et al 2009;Ross et al 2013, for similar parametrizations). The luminosity evolution is achieved by allowing L * to change with redshift, log L * (z) = log L0 − log 1 + zc 1 + z…”

Section: Parametermentioning

confidence: 99%

“…Our approach differs from most prior studies of the evolution of the XLF, which instead attempt to find a model that directly describes the total XLF, either using an LDDE parametrization or some form of luminosity and density evolution (e.g. Ebrero et al 2009;Yencho et al 2009;Aird et al 2010). …”

Section: Comparison With Previous Studies Of the X-ray Luminosity Funmentioning

confidence: 99%

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The evolution of the X-ray luminosity functions of unabsorbed and absorbed AGNs out to z∼ 5

Aird

Coil

Georgakakis

et al. 2015

Monthly Notices of the Royal Astronomical Society

375

559

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We present new measurements of the evolution of the X-ray luminosity functions (XLFs) of unabsorbed and absorbed Active Galactic Nuclei (AGNs) out to z ∼ 5. We construct samples containing 2957 sources detected at hard (2-7 keV) X-ray energies and 4351 sources detected at soft (0.5-2 keV) energies from a compilation of Chandra surveys supplemented by wide-area surveys from ASCA and ROSAT. We consider the hard and soft X-ray samples separately and find that the XLF based on either (initially neglecting absorption effects) is best described by a new flexible model parametrization where the break luminosity, normalization and faint-end slope all evolve with redshift. We then incorporate absorption effects, separately modelling the evolution of the XLFs of unabsorbed (20 < log N H < 22) and absorbed (22 < log N H < 24) AGNs, seeking a model that can reconcile both the hard-and soft-band samples. We find that the absorbed AGN XLF has a lower break luminosity, a higher normalization, and a steeper faint-end slope than the unabsorbed AGN XLF out to z ∼ 2. Hence, absorbed AGNs dominate at low luminosities, with the absorbed fraction falling rapidly as luminosity increases. Both XLFs undergo strong luminosity evolution which shifts the transition in the absorbed fraction to higher luminosities at higher redshifts. The evolution in the shape of the total XLF is primarily driven by the changing mix of unabsorbed and absorbed populations.

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Section: Parametermentioning

confidence: 99%

Section: Comparison With Previous Studies Of the X-ray Luminosity Funmentioning

confidence: 99%

The evolution of the X-ray luminosity functions of unabsorbed and absorbed AGNs out to z∼ 5

Aird

Coil

Georgakakis

et al. 2015

Monthly Notices of the Royal Astronomical Society

375

559

View full text Add to dashboard Cite

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“…Page & Carrera (2000) presented an improved method of constructing the binned LF (also see Tzanavaris & Georgantopoulos 2008;Yencho et al 2009). That is, the LF at the center of a bin with a luminosity interval L 1 and L 2 and a redshift interval z 1 and z 2 can be estimated as…”

Section: The P C Methodsmentioning

confidence: 99%

A graphical analysis of the systematic error of classical binned methods in constructing luminosity functions

Yuan

Wang

2013

Astrophys Space Sci

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The classical 1/V a and P C methods of constructing binned luminosity functions (LFs) are revisited and compared by graphical analysis. Using both theoretical analysis and illustration with an example, we show why the two methods give different results for the bins which are crossed by the flux limit curves L = L lim (z). Based on a combined sample simulated by a Monte Carlo method, the estimate φ of two methods are compared with the input model LFs. The two methods give identical and ideal estimate for the high luminosity points of each redshift interval. However, for the low luminosity bins of all the redshift intervals both methods give smaller estimate than the input model. We conclude that once the LF is evolving with redshift, the classical binned methods will unlikely give an ideal estimate over the total luminosity range. Page & Carrera (2000) noticed that for objects close to the flux limit φ 1/Va nearly always to be too small. We believe this is due to the arbitrary choosing of redshift and luminosity intervals. Because φ 1/Va is more sensitive to how the binning are chosen than φ P C . We suggest a new binning method, which can improve the LFs produced by the 1/V a method significantly, and also improve the LFs produced by the P C methods. Our simulations show that after adopting this new binning, both the 1/V a and P C methods have comparable results.

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“…Silverman et al 2008;Aird et al 2008;Yencho et al 2009;Aird et al 2010). More specifically, this incompleteness affects the faint end of the XLF, as its "knee" at z = 2 is at log L x ∼ 44.5 erg s −1 (log L * = 44.4−45.0 erg s −1 depending on the luminosity evolution model, Silverman et al 2008; Fig.…”

Section: X-ray Luminosity Function Incompletenessmentioning

confidence: 99%

“…We note that in most cases in the literature the incompleteness caused by optically non-detected sources is treated by either taking an optically bright sample which is spectroscopically complete, with the side effect of undersampling the high redshift -low luminosity cases (e.g. Yencho et al 2009), or using simplistic assumptions, like that their redshift distribution is directly connected to their X-ray flux (e.g. Silverman et al 2008), which is generally not true, or treating the incompleteness as a free parameter when fitting the datapoints to determine the luminosity function evolution (e.g.…”

Section: X-ray Luminosity Function Incompletenessmentioning

confidence: 99%

Optically faint X-ray sources in the Chandra deep field North:Spitzerconstraints

Rovilos

Georgantopoulos

Akylas

et al. 2010

A&A

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We investigate the properties of the most optically faint sources in the GOODS-N area (R AB > 26.5). These extremely optically faint populations present an uncharted territory although they represent an appreciable fraction of the X-ray sources in the GOODS-N field. The optically faint sources are believed to contain either red active galactic nuclei (AGN) at moderate redshifts or possibly quasi stellar objects (QSOs) at very high redshift. We compile our sample by first finding the 3.6 μm IRAC counterparts of the X-ray sources and in turn by searching for the optical counterparts of the IRAC sources. No counterparts were found for 35 objects in the R-band Subaru optical images. Of these, 18 have HST ACS counterparts, while the remaining have no optical counterparts. The vast majority of our 35 sources are classified as extremely red objects (EROs) on the basis of their V 606 − K S lower limits. Their derived photometric redshifts show that these populate moderate redshifts (median z ∼ 2.8), being at markedly different redshifts from the already spectroscopically identified population which peaks at z ∼ 0.7. The Spitzer IRAC mid-IR colours of the sources without HST counterparts tend to lie within the mid-IR colour diagram AGN "wedge", suggesting either QSO, ultra luminous infrared galaxy (ULIRG; Mrk231) templates or early-type galaxy templates at z > 3. A large fraction of our sources (17/35), regardless of whether they have HST counterparts, can be classified as mid-IR bright/optically faint sources (dust obscured galaxies) a class of sources which is believed to include many heavily absorbed AGN. The co-added X-ray spectrum of the optically faint sources is very flat, with a spectral index of Γ ≈ 0.87, significantly flatter than the spectrum of the X-ray background. The optically faint (R > 26.5) X-ray sources constitute more than 50 per cent of the total X-ray population at redshifts z > 2, bearing important implications for the luminosity function and its evolution. Considering X-ray sources with 2 < z < 4 we find good agreement with a modified pure luminosity evolution (PLE) model.

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THE OPTX PROJECT. II. HARD X-RAY LUMINOSITY FUNCTIONS OF ACTIVE GALACTIC NUCLEI FORz≲ 5

Cited by 83 publications

References 58 publications

The evolution of the X-ray luminosity functions of unabsorbed and absorbed AGNs out to z∼ 5

The evolution of the X-ray luminosity functions of unabsorbed and absorbed AGNs out to z∼ 5

A graphical analysis of the systematic error of classical binned methods in constructing luminosity functions

Optically faint X-ray sources in the Chandra deep field North:Spitzerconstraints

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